This invention relates to the preparation of unsaturated nitriles from olefins, and more particularly to the vapor phase ammoxidation of propylene or isobutene, respectively, to acrylonitrile or methacrylonitrile in the presence of catalysts based on the combination of antimony, tin, copper, and tungsten.
It is known in the art, particularly from French Pat. Nos. 1,299,139 and 1,293,088, that catalysts based on the oxides of antimony and the oxides of tin permit production of unsaturated nitriles from olefins. It has been stated in other patents, particularly in Certificate of Addition 81,246 to French Pat. No. 1,299,139 and in French Pat. Nos. 2,176,770 and 2,176,771, that the oxides of polyvalent metals such as iron, copper, vanadium, titanium, calcium and barium can be advantageously used with the oxides of antimony and of tin to oxidize propylene to acrylonitrile in the presence of ammonia.
Other combinations of oxides of polyvalent metals with oxides of antimony and of tin have been shown in a very general manner in various patents as French Pat. Nos. 2,020,512 and 2,065,317, and British Pat. No. 1,280,073. Certain of these combinations, in particular those shown in French Pat. No. 2,176,771, provide a high rate of conversion of propylene to acrylonitrile, but they necessitate relatively lengthy contact times which result in insufficient productivity for industrial needs.